This subject matter herein generally relates to an imaging system and more particularly to a method and system for controlling an intensity of a radiation beam employed in the imaging system. The method and system for controlling radiation intensity may be used in applications related to medical and industrial imaging.
A certain conventional radiation imaging system generally includes an radiation source configured to project a beam of electromagnetic radiation toward a subject being imaged. The radiation beam is typically collimated so as to pass through a region of interest of a subject being imaged, such as a patient. As the radiation beam passes through the imaged subject, the imaged subject attenuates the radiation beam intensity. Upon passing through the imaged subject, the attenuated radiation beam impinges upon an array of radiation detectors. The intensity of the radiation beam received at the array of radiation detectors is dependent upon the attenuation of the X-ray beam by the imaged subject. With a conventional digital type of radiation detector, each of an array of radiation detector elements, or pixels, produces a separate electrical signal that is a measurement of the attenuation of the radiation beam intensity at that location of the radiation detector. The attenuation measurements from all the detector pixels are acquired separately to produce a transmission profile. In fluoroscopy, such beam attenuation measurements are repeated successively to create a real-time video of the radiation projection of the imaged subject.
However, conventional radiographic or fluoroscopic imaging systems have drawbacks. For example, a typical radiation intensity across a cross-section of an initial radiation beam from a conventional imaging radiation system is nearly uniform such that the imaged target can receive a radiation dose irrespective of the varying thickness of the target, regardless of movement of the subject being imaged, and/or regardless of the area of most interest to the operator.
A sufficiently high dose of radiation intensity is typically transmitted through the imaged subject so as to ensure that, after interacting with the imaged subject, the attenuated radiation leaving the imaged subject will have sufficient number of X-ray photons to reach the radiation detector and produce an image with sufficient contrast. However, exposure to reduced intensities of radiation may only be needed to adequately image an area of interest (e.g., thinner portions) of the image subject, or to acquire an image for reference only that does not require high spatial or gray scale resolution, or where little change occurs from frame to frame of the imaged subject.